Polycarbonate resins are prepared by condensation-polymerization of an aromatic diol such as bisphenol A with a carbonate precursor such as phosgene and have excellent impact strength, dimensional stability, heat resistance and transparency. Thus, the polycarbonate resins have application in a wide range of uses, such as exterior materials of electrical and electronic products, automobile parts, building materials, and optical components.
Recently, in order to apply these polycarbonate resins to more various fields, many studies have been made to obtain desired physical properties by copolymerizing two or more aromatic diol compounds having different structures from each other and introducing units having different structures in a main chain of the polycarbonate.
Especially, studies for introducing a polysiloxane structure in a main chain of the polycarbonate have been undergone, but most of these technologies have disadvantages in that production costs are high, and when chemical resistance or impact strength, particularly impact strength at low temperature are increased, the melt index or the like are conversely lowered. Therefore, in order to improve various physical properties simultaneously, the chemical structure of polycarbonate, the mobility of the polycarbonate chains and the like should be multilaterally considered. In the present invention, the mobility of the molecule was analyzed through a TD (Time-domain)-NMR FID experiment.
Important NMR information that appears on the FID signal pattern is T2 relaxation time, which appears the difference depending on the flexibility of the molecular structure, and the decay rate changes in the FID signal accordingly. In other words, the more rigid the molecule, the FID decay rate is faster. Also, the more flexible the molecular, the FID decay rate is slower.
In this regard, the present inventors have conducted TD (Time-domain)-NMR FID analysis of a copolycarbonate composition comprising a copolycarbonate in which a polysiloxane structure is introduced in a main chain of the polycarbonate, and optionally a polycarbonate, and prepared a copolycarbonate composition which has various excellent physical properties.